The present invention relates to a control apparatus for a gas analyzer system applicable, for example, to an automobile exhaust gas analyzer and a control method thereof.
In general, a gas analyzer system such as an automobile exhaust gas analyzer is required to be composed of a plurality of gas analyzers to measure various kinds of gases such as CO, CO2, THC, and NOx. The gas analyzers include a nondispersive infrared analyzer (hereinafter to be referred to as NDIR), a flame ionization detector (hereinafter to be referred to as FID), chemi-luminescent detector (hereinafter to be referred to as CLD), etc. Thus, multi-component gases to be measured such as automobile exhaust gas have so far been analyzed by a gas analyzer system comprising a plurality of gas analyzers for analyzing the specific gases and the gas analyzer processors connected to those gas analyzers.
FIG. 2 is a block diagram to show the control apparatus for the conventional gas analyzer system 20. In FIG. 2, the gas analyzer system 20 comprises an analyzer processor 21, analyzers 22-24 for analyzing respectively different specified gases, and cables 25 for connecting the respective parts 21-24.
The analyzers 22-24 respectively have analyzer substrates 26-28 and analyzers 30-32, and the respective analyzer substrates 26-28 are provided with CPUs 26a-28a and non-volatile memories in which the programs for operating the CPUs 26a-28a are written (hereinafter to be referred to as ROM) 26b-28b. In other words, in this gas analyzer system 20, due to the provision of the CPUs 26a-28a on the respective analyzers 22-24, individual controls of the analyzers 30=32 are made by these CPUs 26a-28a. By mediating the inputted measuring signals through the communication part 29 and the cables 25, the signals are transmitted to the analyzer processor 21.
On the other hand, the analyzer processor 21 is provided with the CPU 21a and the ROM 21b, in which the program for operating the CPU 21a is written, so that it is possible to calculate the concentration value of various kinds of gases by processing the measuring signals inputted through the communication part 29, and to display the results on the screen 21d or the like by outputting the results to the display processor 21c or the like.
Because the constitutions of the respective analyzers 30-32 are respectively different, the above analyzer substrates 26-28 are provided with the AD converters 26c-26g, 27c, 27d, 28c-28f for inputting the analog signals outputted from various gas analyzers A of the respective analyzers 30-32 and sensors S. The AD converters 26c, 26d, 27c, 28c, 28d are each an AD converter having one analog input port, making it possible to input the analyzing results from the gas analyzer A at a high speed. On the other hand, the AD converters 26f, 26g, 27d, 28e each has a multiplexer for changing over the four analog input ports, to which the measured values are inputted at a relatively low speed from the sensors for determining the sample flow amount, change in source voltage, temperature, etc. In the AD converter 26e or 28c which is provided with two or three analog input ports, the measured values are inputted at an intermediate speed.
Furthermore, the AD converters 26c-26g, 27c, 27d, 28c-28f self-contain respectively an amplifier for gain adjustment, being so constituted as to convert the measured values inputted from the analyzers 30-32 appropriately to digital signals.
Accordingly, the CPUs 26a-28a are to carry out individually the gain adjustments of these AD converters 26c-26g, 27c, 27d, 28c-28f and control of the input speed of the measured values in conformity with the number and characteristics of the gas analyzers A and various sensors S in the analyzer units 30-32.
The gas analyzer system 20 as described above controls the analyzer units 30-32 in the unit of the analyzers 22-24, so that it describes the hardware information inherent to the analyzers 22-24 as the programs for the individual CPUs 26a-28a. Accordingly, it has been necessary to compose programs for the individual analyzers 22-24 to give different operation commands to the respective CPUs 26a-28a, write these programs in the ROMs 26b-28b, and set them to the analyzer substrates 26-28. For this purpose, when a new type of apparatus having the analyzer units 30-32 having different number of sensors and performance is manufactured, the number and performance of the AD converter are required to be changed, for which it becomes necessary to redesign the whole analyzer substrates 26-28 or newly recompose the program for the CPUs 26a-28a, requiring a great deal of time and labor.
Above all, in the case of making a version of the gas analyzer system 20 which is already in use by the customers, when a change has been made in the number of the input signals from the analyzer unit or characteristics due to the improvement of the analyzer units 30-32, it requires time for the work of rewriting the programs written on the ROMs 26b-28b, and the version-up work is laborious.
In view of the above, it can be considered to make programming in a manner to make direct control of the analyzers 30-32 and AD converters 26c-26g, 27c, 27d, 28c-28f in CPU 21a in the analysis processing unit 21 and to write the program in the ROM 21b. However, when there are provided plural programs for controlling plural analyzers 22-24 in one CPU 21a, inversely it becomes necessary to modify the whole program for the sole purpose of changing the control method of one analyzer. In addition, because the control programs for the analyzers 30-32 include many common portions, to change only a part of the programs for making the similar processings tends to induce the generation of erroneous programming, leading to a danger of changing the control programs of other analyzers which need not be changed, thus making the controls more complicated.
The present invention has been made in consideration of the matters described above. Its objects, are to provide a control apparatus for the gas analyzer system for controlling a plurality of analyzers having different hardware constitutions in a single program which works on a single CPU, and a method for its control.
To attain the above objects, the control apparatus for the gas analyzer system of the present invention is characterized in that, in a gas analyzer system comprising a plurality of gas analyzers having gas analyzer units for analyzing respectively specified gases and an analyzer processing unit connected to these gas analyzers, the analyzer processing unit is provided with a CPU which is connected with each gas analyzer by a CPU bus and designed to control each gas analyzer. Each gas analyzer is provided with a plurality of AD converters having respectively a plurality of analog input ports in which the respective output signals of the gas analyzer units are inputted, and a non-volatile memory unit for storing the connection condition table which shows the connection condition of the gas analyzer unit to these AD converters. By connecting to the CPU bus, the CPU in the analyzer processing unit can control the respective gas analyzers by a single program.
The control method of the gas analyzer system of the present invention is characterized in that, in a gas analyzer system comprising a plurality of gas analyzers having gas analyzer units for analyzing respectively specified gases and an analyzer processing unit connected to these gas analyzers, and being provided with a plurality of AD converters having respectively plural analog input ports in each gas analyzer and a non-volatile memory unit irrespective of the kind of the gas analyzer, a table of connection conditions to show the input condition of the output signals of the gas analyzer unit to the analog input port of each AD converter is stored in the memory unit. The signal which is inputted to the AD converter in each gas analyzer above is read out by the CPU in the analyzer processing unit while referring to the connection condition table stored in the memory unit, thereby reading out the analog input from the gas analyzer unit which outputs respectively different signals by a single program irrespective of the kind of the gas analyzer to control each gas analyzer.
Accordingly, by referring to the above connection condition table, the CPU in the analyzer processing unit can regard the different analyzers in the analyzer means (gas analyzer unit) to be identical. In other words, because of the fact that the plural analyzers can be appropriately controlled using a single program working on a single CPU, even in case the gas analyzer system covers diversified kinds of analyzers such as NDIR, FID, CLD, etc., control can be made by a single program, and simplification can be obtained.
Further, in each gas analyzer, because the hardware information inherent to the analyzer is controlled in the form of a table, even in case of upgrading of the gas analyzer unit, the system can be coordinated simply by writing the table of connection condition coordinates with the new gas analyzer unit in the memory unit or replacing with the memory unit in which the above connection condition table is written. In other words, because the system operation can be met simply by alteration of the connection condition table even in case of the change of the hardware of gas analyzer, there is no necessity to rewrite the program to the CPU in the analyzer processing unit.
Furthermore, as there is no necessity to load a CPU in the unit of the gas analyzer, the constitution of the analyzer substrate of each gas analyzer can be simplified. In addition, by sufficiently providing the number of the AD converters, the analyzer substrates in the gas analyzers can be commonly designed utterly irrespective of the kind of the gas analyzer unit, so that the labor required for the designing can be suppressed as far as possible.
The above connection condition table may be so designed as to have an AD converter changeover table which, when the CPU reads out the signal from each gas analyzer in the unit time, records the plural numbers of the AD converter changeover information carrying the input port number of the AD converter to be read out and the channel number assigned to the input port by the number of the AD converters, and provides one of the plural kinds of AD converter changeover information sequentially per unit time.
In this case, the CPU may appropriately change over the input port of the AD converter to meet the connection condition with the gas analyzer unit so as to make it possible to read out the required measuring signal and regulate the reading speed of each measuring signal inputted from the gas analyzer unit.
The above connection condition table may have the channel information table which has records of the channel specific information of the number of channels containing the channel specific information having respective channel numbers, numerical amount which shows the magnitude for gain adjusting the analog signal inputted to the channel in an AD converter, a flag to show if the spike noise is included in the analog signal, a flag to show whether it is necessary to make gain correction on the CPU side or not, and the numerical value showing the measuring space.
In this case, the CPU can appropriately process the measuring signal of each channel inputted from the gas analyzer unit and calculate the concentration of the measured gas, and also optionally control the AD converter in tune with the analog measuring signal inputted to each channel.
The connection condition table written in the memory unit as described above shows the minimum necessary information for indicating the connection condition of the hardware inherent to the respective analyzer, and correspondence of the connection condition table to the hardware connection condition is easy to understand. Accordingly, in comparison with the individual setting of the program conforming to the hardware of each gas analyzer unit, the information amount to be memorized is exceedingly small and the corresponding relations between them are easy to understand. Consequently, it is possible to suppress as much as possible the generation of errors in case of development of a new type of apparatus or upgrade of the system.